Field coil construction



July 24, l1951 R. E. FIERRIS Erm. 2,56l`-,352

FIELD COIL CONSTRUCTION Filed Aug. 19, 1948 ATTORNEY Patented July 24, 1951 FIELD `COIL `CONSTRUCTION Ralph E. Ferris and Maurice F. Jones, Pittsburgh,

Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 19, 1948, Serial No. 45,128

4 Claims. 1 Our invention relates generically to electric machines, but it was designed for, and has more particular relation to, the main-eld winding of a series commutator dynamo-electric machine of a Vtype which is provided with interpole windings as well as main-held windings. Still more particularly, our invention relates to single-phase series commutator-motors such as are used for traction-purposes in electric-railway practice.

The stator-windings for single-phase series commutator motors have always been dicult and very expensive to make and assemble, on account of the slot-arrangements which are necessitated by the electrical design.

Our invention is an improvement over the sub- Y ject-matter of a copending application of Carl H.

Sutherland, Serial No, 39,321, led July 17, 1948, which covers a novel type of slot-arrangement, and a novel type of split main-field coil which was considered necessary in order to make the coil-assembly.

It is an object of our present invention to provide a main-field coil which is composed of a plurality of thin (and therefore flexible) copper conductors which are connected either in series, parallel, or series-parallel as may be dictated by the Voltage-requirements. It is a characteristic feature of our invention that each main-iield coil is pre-formed and completely insulated before being placed in the stator-slots of the motor; and the coil-sides, or portions of the coil which are to lie in the slots, are given the usual impregnationtreatment and hardening-treatment which is necessary to withstand the voltage-strain from the conductors to the core-laminations; while the end-portions of the coil, as pre-formed, are not given any impregnating and/ or heating treatment which would harden them, so that these endportions of the coil remain flexible, due to the stranded construction, thus permitting the coil to be spread temporarily for the purpose of passing over the main-pole tips in the process of assembly, after which said end-portions may be given any necessary additional insulating treatment.

With the foregoing and other objects in View, our invention consists in the combinations, systems, methods, machines and parts, hereinafter described and claimed, and illustrated in the accompanying drawing, wherein:

Figure l is a conventional diagrammatic view of a series interpole single-phase commutatormotor of the type to which our invention applies;

Fig. 2 is a fragmentary transverse-sectional view of aportion of the stator-member, showing,

vin full lines, a sectional view of a main-field coil in its final position, and also a guiding-block or tool which is useful in getting said coil into position, and showing, in dotted lines, two intermediate positions of the same coil; and

Fig. 3 is a plan-view diagram of a preformed main-field coil, with a dotted-line indication of the spread condition which it assumed in the process of getting it into position in the motor.

By way of concrete illustration, our invention is shown, in Fig. l, as being applied to a type of single-phase commutator-motor having a stationary member including a main-field winding 5 and an interpole-winding 6, said motor also having a rotatable commutator-type armature-winding 1. which is schematically or diagrammatically indicated by means of a single circle l, which represents both the armature-core, the armature-Winding, and the commutator which is associated therewith. The held-member 5 6 and the rotormember 'I are separated by an airgap 8. Brushes 9 bear on the commutator. The motor in Fig. 1 is supplied with electrical power from a singlephase line LIL-L2, which serially includes the interpole-winding 6, the main-held winding 5, and the armature 1.

As shown in Fig. 2 of the accompanying drawing, and as described and claimed more particularly in the Sutherland application, the stationary held-member, which carries the field-winding 5 and the interpole-winding 6, also includes a stator-core I I which is made up of a stack of statorpunchings, the airgap-periphery of which is provided with slots I2, between which are the stator teeth The stator teeth are of two kinds, alternating between small, straight-sided teeth which constitute the interpoles I3, and larger teeth which constitute the main poles I4 and Which have pole-tips It' in the pole-face portions at the airgap 8.

The pole-arrangement just described makes the slots I2 have a special shape, with the slots disposed in back-to-back pairs of slots, with the so-called backs of each pair of slots in the form of straight, open, slot-portions I5 which are disposed on opposite sides of an intervening interpole I3 of the stator-core II. These open slotportions are open to the gap 8, or to the periphery of the core which faces the rotating armaturemember 'I of the motor. Each of the slots I2 also has an enlarged front portion I6, by which we mean a portion which extends away from the intervening interpole I3 which is disposed between the two slots of a given pair of back-to-back slots. These front slot-portions I6 have no slot-opening other than the slot-opening I'I of the iaspreading and winding 6 of Fig. 1 consists of a like numberrfof interpole-coils, each encircling one.of.the interpoles I3. The two sides of any interpole I3 are parallel to each other, so that wnolproblem is involved in getting the variouscoilsontheiinterpole-winding 6 into place, once thermaineld coils have been assembled on the field-core II.

In accordance with our inventionVtheamamfield coils 5' are pre-formed of a stranded construction, composed ofma plurality of'thinrcopper straps or square wires 20, as shown in Fig.

coil-sides, or straightvside-portions betweeni the l1inest2l `and'z! Yofiig. 3, lief in- -the-slotsfand are f given the usual impregnationetreatm'ent. and hardeningetreatment which-is commonly givento `pref-formed coils toA` make them withstand'. the

voltage-strain `from the conductors .20 -to the Vicore-lamin'ations I I i bordering -thevslot"-fronts In accordance with our invention,- however, theV end-portions l' 23- `of ourr mainf'leldl1 coils 15 'fingl treatment lwhich would f harden theseff end- 'portions inthe pre-formed condition of 'vthe'cils f'yb'efore they-are placedifin the stator-"slotsIfIZ,

Inassembling the stator-windings, the maineld 4coils 5"- are first `put iriplace,A andth'enthe --coi1s-of the interpole-windingnare slipped-over i the'paraIIel-Sided interpoles I3. flniordento get vthecmainefleldy `coils `a1-into: place,A the.' coil-sides 4`-must be spread" temporarily',for` the `purpose Aof passing over the -mainpole tips -"I4;asfshown in Fig. 2. To assist in getting the'fco'ilesidescver thepole-tipsyweprefer to vuse suitablespreaders "or" guiding-forms 24, to actlike shoe-horns,

asfshownfin Fig.v 2. "The pre-formed'c'oil'lff may initially; asfshown, rhave *thelformrr'whichlit--is "'1flnal1y to have,1in its iinal position on theshank- -portion of aimaineld pole I4;Y as shownfin dotted #down intoplace, they guide or spreader spreads Athe coil-'sides apart; so that'ltheyl'pass overf'the `4pcie--tips III` and into the fback" portionsHlSI oflthe'slots, as shown in-dottedilinesatll25f=fin fFig; 2, after which the coilsides snapipartially the front portions I6 of "thelslotsin snug-engagement with the pole-shank portionssoi the #main poles I4, as shown -inpulll lines in 'Thentemporary guide or spreaderld rriaythen 1 1beremoved- The spreading `apart-cf the: .coilasides-lof .our

coil is ,accomplished with f relativeeease, iduei ato .f

the fact that .the individual` straiiiisn!I1y `ofacop- Liperl in; each end-portion 23.1Jofthe 2coil"-may retain theirV originali overall :lengthiduring )the retracting of `-'the coiltsides Thum-there Yis no stretchingfon buckling iofzaany l strand This mathematicalrelationxis shown-,by ;-"F,\ig.. 3,zfrom which/.it4 is` vclearigthat:athewirrtial wlandrnal) glengtlr` of the: outer strand i'of 4 panded is AED' or 1r(Rz+W)-IS, and these two lengths will be equal if 1r(R1-Rz) :SL Similarly, the initial (and nal) length of the inner strand BFC of the end-Winding 23 is 1rR1, while 5 the length of the same strand when the coil is expanded is BFC or 1rRz-I-S, so that these two lengthsa will also" be-equaliunderzthe same condition, namely when v1r(R1-'Rz)i='--S. Therefore, there is no stretching or buckling of any -strand of the end-turns 23 when the coil is ex- .pandedfor retracted.

However, the strands 20 of the end-turns 23 #must 1@slideA along one another a small amount when-*ther coil 'is expanded or retracted, and ihenceyin orderto. retain flexibility, the end-portions23` of `the 'pre-formed main-field coil i ,Immtcnnttbe varnish-impregnated with an adherent varnish until the coil has been passed `rwe1"i'.he pole-tips I4 into the stator-slots I2. Varnish-treatment after the winding-operations f `areficomplete ism-considered: adequate rior-these Vendiqiiontions `i. 3.

tMainFfield coils, `made Ain accordance with; `the 1 principle, fjust f described, mayfhave eithenfmany 2514 turns f per coil, or only. a few turns-f .per-*coilff-.as -fconditions` may require. v/Wheny Irrnanyf turns@ are wreqiiired,c .say 4.from 15.' #to perhaps 40 :turnsi per rcoil, as in alternatingcurrent f railway-motor practica-each turnI may be composed 'eithercof a" single .small conductor yor fstrar'id,v or oi*l a'- few lstrandsi l1in parallel, r and allf of fthe4 fcoi1s'f`5`of lfthei-:main-Iield Winding 5 'rwould 'bef' commonly connected: in=multlpley .i iIn `a .motorfhaving only a few turns per coil, each.-\tumwould beecomi posed.V of u several f.- strands 1 in multiple, 1 and* the .vcoilsfwould `be i connected either all` fin 'series' or =r possiblydnftwo or three .multiple paths.

mln; either Vof these .two "types of v` coils,"fi'the z amount 1 'of i '.strariding,y ink both :the radial andilat- 40H eral (or circumferential) directions,'mustbe `siii?- cient to give the required degree=of-exibilityv:'lhe` .foregoing-s andotherchangesmay be=made i :in the coilde'sign, :withoutdepartingtfromrlthe cessential spirit `wof our i invention. "We idesire, 4, 5 ntherefore, 'that the appended claims "shall ibamoffcorded-'vthe:broadest .scope .of interpretation cwhichfis consistent vvwith theirlanguage.

,We` claim` as our: invention:

i 1.':1An electric machine :having a -frelativeixssta- 501:;tionaryc memberiand a .relatively movableimember separated byr a gap, one of saidmembers'-be l zing` u characterized.' by? having a slotted magnetl :,:izable:.corefsaidwslotsdeilning 4 paralici-sided'1in- :atenpoles i iinterspersed" between f `=main-fieldyf-poles :having shank@portions"I and =-pole-'tips, amminl'itields-,winding ihaving preformed" coils iitting'virer `isaidfpolel-tips 'and onto *the shankeportions A1of tithe imam-field poles;Vl and an ``interpole-iiririding f having coils disposedon-lsaid -interpoles andhoidling` the side-portions of saidmainl-eldccils uin Vplace on `the main-fieldv shank-portions.

2.' lThe` 4invention `as ydefined: in 'i claim lj'characterized` "by# eachfof saidmaineeldcoilsbeing composed of a4 plurality A of thinjifiexible-conduc- 651` corsiv fhavingllstraight i' coil-sides which are "com- :fpletely Linsulated' and hardened, and `ln`a,vii1g'-'!iex i fible endeturn portionsvin which, `in Ihtheprefcrm'ed f, conditioner` the coil l it fisf possible;v lfor the 'different strands to have a` small `amountifoi"end- 7 owwiseislippage; overfeaclr Iotheras the preformed :coil is Y eiscpandedY or: retracted; =inf fthe processf'fo! i inpassing; :the: coil 1over:` the: pole-tips :laut` `series,wcommutatorl.iiynamoelectricfimaachinelwhaving a-reiatiively stationaryv held-mem- Naber-.landtacelatiyely'rotatablearmature-fmemker having a commutator associated therewith and being separated from said held-member by an airgap, said held-member having more than two poles and comprising a stack of magnetizable punchings having a plurality of slots on their airgap-periphery, said slots defining parallelsided interpoles interspersed between main-field poles having shank-portions and pole-tips, a main-field winding having preformed coils fitting over said pole-tips and onto the shankportions of the main-field poles, and an interpole-winding having coils disposed on said interpoles and holding the side-portions of said main-eld coils in place on the main-held shank-portions.

4. The invention as dened in claim 3, characterized by each of said main-held coils being composed of a plurality of thin, flexible conductors, having straight coil-sides which are completely insulated and` hardened, and having REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 907,891 Sulzberger Dec. 29, 1908 949,106 Wright Feb. 15, 1910 1,158,598 Walker Nov. 2, 1915 1,697,134 Neely Jan. 1, 1929 zo 1,697,138 Prantl Jan. 1, 1929 

